1. Field of the Invention
This invention relates to a fuelling apparatus used in fuel depots. It is particularly useful in preventing supplying incorrect type of fuel to a vehicle utilizing liquid type fuels from a pumping station.
2. Background Art
In general, in fuel depots, different types of fuels are supplied from different pumping stations, each equipped with a fuel flow meter and a nozzle to deliver the liquid fuel to a vehicle.
The fuelling operation incorporates steps to ascertain that the type of fuel, to be supplied to a particular vehicle, matches with that of the type of fuel contained in that particular station before the actual pumping operation can begin.
The procedure for deciding whether or not the fuel in the pumping station matches with that required by the vehicle is as follows:
A pumping station is equipped with two types of hoses extending side by side in parallel with each other; which are,
1. a hose to deliver the fuel to a fuel tank of a vehicle requiring the fuel, and
2. a hose to exhaust the vapors present in the said tank of the said vehicle.
Furthermore, each pumping station is equipped with two types of devices to carry out the objective of confirming that the fuel contained in the pumping station matches with the fuel requirement of the vehicle; the two types of devices are,
1. a sensing and measuring device, sometimes referred to as a sensor, to measure the concentration of the vapors emitted by the fuel, and
2. a device to identify the type of fuel based on the information obtained from the magnitude of the concentration determined by the said sensing device
When a nozzle of the fuel supply pump is inserted into the fuel tank of a vehicle, the first step is the removal of the vapor from the fuel tank of the said vehicle through the vapor intake pipe, and the measurement of the concentration of the fuel vapor contained in the said tank, using the said sensing device.
Such sensors are often made of semiconducting metal oxide materials.
The said semiconducting metal oxide materials, referred to hereafter as oxide semiconductor, undergoes changes in the electrical conductivity when the vapor molecules are absorbed on the surface of the oxide semiconductor. The said identifying device determines the type of fuel in the fuel tank from the magnitude of the changes in the electrical conductivity which takes place on the said sensing device.
The conventional pumping stations have the following problems associated with their reliability.
The said identifying device determines the type of fuel based on the electrical output of the said sensing device, the magnitude of the signal therefrom is attained by electronic amplification of the signals from the said sensing device.
In general, gasolines produce high magnitude signals while light oils produce low magnitude signals. Therefore, based solely on the concentration factors, the said identifying device judges the fuel type to be gasoline when high magnitude signals are presented by the sensing device while the said identification device judges the vapor to be light oils when low magnitude signals are presented thereto.
This methodology, based solely on the magnitude of the signals, has a serious problem in accurately defining the type of fuel, because a malfunctioning electrical circuit may, at times, lead the identification device to interpret erroneously that low magnitude signal, produced by the defective circuit, is generated by a light oil.